Grassland weeds are now evident in a lot of swards subjected to severe drought stress last summer.

The reason is that weeds are opportunists - their seeds are in the soil all the time and they are just looking for sunlight and the correct conditions to grow.

Germination

With grass under severe pressure last summer and with swards grazed bare, weeds got the opportunity to germinate.

Once established in the sward, weeds can have a significant impact on grassland performance.

Firstly, if we consider the price of nitrogen (N), phosphorus (P) and potassium (K), allowing weeds to use up those nutrients has a big cost impact.

Furthermore, weeds will also reduce the performance ability of animals grazing the sward rendering our output targets far less achievable.

Without doubt, an integrated weed management approach is best.

Grazing management, topping and alternating grazing and silage ground should come first, with a herbicide being the last option.

Docks

Best control of docks will be achieved in good growing conditions when docks are actively growing and nutrients are actively being transported to new foliage and roots.

If seed stalks are seen on the plant or if the dock has diseased leaves or is under pest attack, it is better to cut/top or graze and allow re-growth of the docks before applying chemical.

The use of herbicides based on aminopyralid, dicamba, triclopyr, fluroxypyr, etc, will give at least season-long control (possibly two to three years significant reduction in numbers and regrowth of docks) plus a wide range of common grassland weeds.

Ragwort

Ragwort is poisonous in the green and preserved state and has been responsible for many animal fatalities.

Normally, animals do not eat ragwort in pastures unless grazing is extremely restricted, while research suggests that an animal must consume up to 12% of the animal’s body weight to cause problems.

However, where ragwort is present within finely chopped silage, animals are forced to eat it, causing most fatalities.

It becomes more palatable to animals when cut or sprayed, as it releases sugars.

Any control strategy should be based on the fact that ragwort is a biennial (lives for two years) and also that just because you killed it with a spray does not mean it cannot harm livestock.

Small numbers of ragwort can be effectively pulled or dug up and safely removed.

For larger numbers, sprays such as MCPA, 2, 4-D, Dicamba, Thrust and Forefront provide good control, but measures must be taken to avoid stock eating any dying or dead ragwort present. Best time to spray ragwort is before the flower stem elongates.

Cattle in ragwort and thistles.

Creeping thistle

Creeping thistle is a perennial plant and grows mainly from an underground stem or rhizome and this makes total control difficult with one spray.

Yield losses of up to 15% have been recorded, but they cause most damage by preventing animals grazing around them.

Frequent topping can reduce the root reserves, but will seldom eradicate the problem, as root fragments can lay viable and dormant for years.

This weed is best sprayed with Thisltlex, Forefront, MCPA or 2, 4-D in June before flowering and may need a second treatment later in the season to control any late shooting thistles.

In a reseed, both root fragments and seed can cause an explosion of creeping thistles.

Spear thistle

Spear thistle only spreads by seed. Each plant lives for two years (like ragwort) producing a flatted rosette of leaves in year one and then the familiar tree-like structure in year two.

Once controlled in the re-seed, it is rarely a problem in grazed fields except after poaching or other sward damage.

Topping is not effective to control the growth in year one of their life cycle (as the thistles are under the cut level). but can be carried out on the second year growth before seed is set. Chemical control options are the same as for creeping thistle.

Perennial nettle

Perennial nettle tends to grow in clumps in pasture and can prevent grazing.

The growth pattern of this weed makes it an ideal target for spot treatment with one of the dicamba/triclopyr/fluroxypyr/aminopyralid-based products.

If the clumps are small and not too dense, some of the dicamba/CMPP-based products will also contain them if sprayed on a regular basis. Treat before seed production for best effects.

Soft rush

Soft rush is the most common of the many rush species in this country.

Draining of such infested areas is essential if any herbicide programme is to be successful.

Soft rush can be controlled with MCPA or 2, 4-D applied in June or July when growth conditions are good.

Cutting and removal of the rush about three weeks before spraying will give the best results.

A wetting agent can improve the spray sticking to the slender rush.

Ideally, keeping animals off treated areas allows the grass to recover and prevent new rush seeds from establishing.

Common chickweed

Chickweed

Common chickweed is an annual weed and only spreads by seed.

However, it can germinate and set seed throughout the year, making it seem a perennial weed (lives for many years).

It is a low ground-hugging weed and its fast growth allows it to become established, especially after re-seeding.

It has been shown to reduce silage yields and quality.

The key to its effective management is to get the grass sward established rapidly to smother out the chickweed.

Late-sown and poorly established reseeds are likely to have chickweed problems.

In old pastures, there are many excellent chemical options available, but the holes left after killing the chickweed are ideal for more seeds to germinate, continuing the problem.

Fluroxypyr/CMPP/Dicamba/Aminopyralid offer very good control, but dense patches may need a second spray due to coverage issues.

Sustainable Use Directive

All farmers that apply pesticide must be registered as a professional user and have completed the pesticide application module.

When spraying, remember to keep a record of the products used, when and where they were applied, and the concentration at which they were used.